ALPHA MODIFICATIONS
- exxos
- Site Admin
- Posts: 13269
- Joined: Wed Aug 16, 2017 11:19 pm
- Location: UK
- YouTube: https://www.youtube.com/user/exxosuk
- Contact:
ALPHA MODIFICATIONS
Started a new thread for "must do" fixes and mods etc.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
- exxos
- Site Admin
- Posts: 13269
- Joined: Wed Aug 16, 2017 11:19 pm
- Location: UK
- YouTube: https://www.youtube.com/user/exxosuk
- Contact:
Re: ALPHA MODIFICATIONS
JUMPER PADS
SJ1 & SJ2 are the 2 solder pads like on the STFM near the blitter. Pads must be shorted when NOT using the blitter, and OPEN when using the blitter. For now I would suggest not fitting the blitter.
SJ5 is the clock line for the CPU, this needs to be soldered to allow 8MHz clock to CPU.
SJ3 & SJ4 Need to both be linked.
(Jumpers were there with intention of adding boosters without cutting tracks at a later date )
Jumper next to the ROM is the TOS104 / TOS102 select line.
SJ1 & SJ2 are the 2 solder pads like on the STFM near the blitter. Pads must be shorted when NOT using the blitter, and OPEN when using the blitter. For now I would suggest not fitting the blitter.
SJ5 is the clock line for the CPU, this needs to be soldered to allow 8MHz clock to CPU.
SJ3 & SJ4 Need to both be linked.
(Jumpers were there with intention of adding boosters without cutting tracks at a later date )
Jumper next to the ROM is the TOS104 / TOS102 select line.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
- exxos
- Site Admin
- Posts: 13269
- Joined: Wed Aug 16, 2017 11:19 pm
- Location: UK
- YouTube: https://www.youtube.com/user/exxosuk
- Contact:
Re: ALPHA MODIFICATIONS
RESET FIX
First is the short as found by icky on the reset circuit viewtopic.php?f=19&t=1171#p9633
The red circle shows the resistor shorting out VCC to the highlighted yellow line..
SOLUTION
STEP 1: Cut the tracks on the bottom of the pcb where the yellow lines are.
STEP 2: Solder a wire on the bottom of the PCB to join the pads highlighted with a yellow circle.
DONE:
First is the short as found by icky on the reset circuit viewtopic.php?f=19&t=1171#p9633
The red circle shows the resistor shorting out VCC to the highlighted yellow line..
SOLUTION
STEP 1: Cut the tracks on the bottom of the pcb where the yellow lines are.
STEP 2: Solder a wire on the bottom of the PCB to join the pads highlighted with a yellow circle.
DONE:
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
- Icky
- Moderator
- Posts: 2720
- Joined: Sun Sep 03, 2017 10:57 am
- Location: UK
- YouTube: https://tinyurl.com/yals4a3k
- Contact:
- exxos
- Site Admin
- Posts: 13269
- Joined: Wed Aug 16, 2017 11:19 pm
- Location: UK
- YouTube: https://www.youtube.com/user/exxosuk
- Contact:
Re: ALPHA MODIFICATIONS

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
- exxos
- Site Admin
- Posts: 13269
- Joined: Wed Aug 16, 2017 11:19 pm
- Location: UK
- YouTube: https://www.youtube.com/user/exxosuk
- Contact:
Re: ALPHA MODIFICATIONS
HSYNC FIX
from here viewtopic.php?f=19&t=1146&start=90#p9961
I ballsed up the Hsync and it needs a fix to bypass the inverter...
from here viewtopic.php?f=19&t=1146&start=90#p9961
I ballsed up the Hsync and it needs a fix to bypass the inverter...
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
- Icky
- Moderator
- Posts: 2720
- Joined: Sun Sep 03, 2017 10:57 am
- Location: UK
- YouTube: https://tinyurl.com/yals4a3k
- Contact:
Re: ALPHA MODIFICATIONS
I just sat down to start doing some work on the board tonight and thought I would tackle this first.exxos wrote: ↑Sun Sep 16, 2018 10:30 pmHSYNC FIX
from here viewtopic.php?f=19&t=1146&start=90#p9961
Fix in place but am still getting horizontal scrolling as per video of boot before fix.
Will take a closer look at the circuit to see whats going on.
Re: ALPHA MODIFICATIONS
After cutting the trace on both sides of R920 ,,,, measure between D7 and the cut free R920 i get zero ohm, those two point must go to positive plane in pcb, so i guess no need to move the R920.
And also i noticed that the holes for the PSU is mirrored on the PCB.. Maybe you already know this..
And also i noticed that the holes for the PSU is mirrored on the PCB.. Maybe you already know this..
- exxos
- Site Admin
- Posts: 13269
- Joined: Wed Aug 16, 2017 11:19 pm
- Location: UK
- YouTube: https://www.youtube.com/user/exxosuk
- Contact:
Re: ALPHA MODIFICATIONS
ahh yep, The left link wire isn't needed as the resistor itself actually connects to vcc.. will update the info...
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
Re: ALPHA MODIFICATIONS
i can see all the chips have a decoupling capacitor,,, but what about BAD DMA ? is there one and where? or is it not necessary?